Golf club set and golf club

ABSTRACT

A golf club set according to the present invention is constituted by a plurality of golf clubs having different loft angles. Each golf club includes a shaft and a golf club head. Each of the golf club heads includes a crown part, a face part, a sole part, and a hosel part attached to the shaft. In at least one combination of golf clubs, among the plurality of golf clubs, having different loft angles, the golf club head of the golf club having the higher loft angle is, when in a reference state, longer from a lowermost point to an uppermost point of the golf club head, excluding the hosel part, than the golf club head of the golf club having the lower loft angle.

TECHNICAL FIELD

The present invention relates to a golf club set and a golf club.

BACKGROUND ART

A golf club set typically includes multiple clubs having different loftangles (JP 2012-61035A, for example). Clubs having low loft angles areused to achieve longer flight distances. On the other hand, clubs havinghigh loft angles are used for shots when near the green, where theplayer often aims for a small area on the green. Clubs having high loftangles put an increased amount of backspin on the ball, which ensuresthe ball will stop on the green and is thus useful.

JP 2012-61035A is an example of the related art.

SUMMARY OF THE INVENTION

However, golf clubs included in past golf club sets have notsufficiently exploited such differences in loft angles for betterperformance, and there has been demand for further improvements. Havingbeen achieved to address this issue, an object of the present inventionis to provide a golf club set, and golf clubs included in the set, inwhich clubs having low loft angles can achieve longer flight distancesand clubs having high loft angles can increase the amount of backspin.

A golf club set according to the present invention is constituted by aplurality of golf clubs having different loft angles. Each golf clubincludes a shaft and a golf club head. Each of the golf club headsincludes a crown part, a face part, a sole part, and a hosel partattached to the shaft. In at least one combination of golf clubs, amongthe plurality of golf clubs, having different loft angles, the golf clubhead of the golf club having the higher loft angle is, when in areference state, longer from a lowermost point to an uppermost point ofthe golf club head, excluding the hosel part, than the golf club head ofthe golf club having the lower loft angle.

In the above-described golf club set, the golf club head of the golfclub having the higher loft angle can have a greater volume than thegolf club head of the golf club having the lower loft angle.

In the above-described golf club set, the plurality of golf club headscan have the same length, in a face-back direction, between a pointfurthest on a face side and a point furthest on a back side, when in thereference state. Note that “the same length” is not limited to beingexactly the same, and includes an allowance of no more thanapproximately 2 mm, for example.

In the above-described golf club set, the golf club heads can be hollowwood types.

In the above-described golf club set, the loft angles of the golf clubheads can be from 16 to 35 degrees.

A golf club according to the present invention is a golf club includedin a golf club set constituted by a plurality of golf clubs havingdifferent loft angles. Each golf club includes a shaft and a golf clubhead. Each of the golf club heads includes a crown part, a face part, asole part, and a hosel part attached to the shaft. In at least onecombination of golf clubs, among the plurality of golf clubs, havingdifferent loft angles, the golf club head of the golf club having thehigher loft angle is, when in a reference state, longer from a lowermostpoint to an uppermost point of the golf club head, excluding the hoselpart, than the golf club head of the golf club having the lower loftangle.

According to the present invention, a club having a lower loft angle canextend the flight distance, and a club having a higher loft angle canincrease the amount of backspin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club head according to anembodiment in a reference state.

FIG. 2 is a plan view corresponding to FIG. 1.

FIG. 3 is a cross-sectional view taken from a line A-A in FIG. 2.

FIG. 4A is a diagram illustrating the boundaries of a face part.

FIG. 4B is a diagram illustrating the boundaries of the face part.

FIG. 5 is a side view of golf clubs, in a golf club set, that havedifferent loft angles.

FIG. 6 is a side view of a #3 utility and a #6 utility taken from FIG.5.

EMBODIMENTS OF THE INVENTION

An embodiment of a golf club set according to the present invention willbe described hereinafter with reference to the drawings. The golf clubsconstituting the golf club set according to the present embodiment areutility type (also called “hybrid type”) golf clubs. The clubs are, forexample, #2 to #6 utilities, having club lengths from 36 to 42 inchesand loft angles from 15 to 35°. As will be described later, the clubsdiffer mainly in terms of the loft angle, the head height (headthickness), and so on. The following will first use a single golf clubas an example to give a general overview of the structures common to theclubs. Then, the differences between the golf clubs in the golf club setwill be described in detail.

1. Overview of Golf Club Head

First, a single golf club in the golf club set according to the presentembodiment (a utility type golf club, for example) will be used as anexample to describe the golf club head. FIG. 1 is a perspective view ofa single golf club head in the golf club set according to the presentembodiment, shown in a reference state. FIG. 2 is a plan viewcorresponding to FIG. 1. FIG. 3 is a cross-sectional view taken from aline A-A in FIG. 2. The reference state of the golf club head will bedescribed later.

As illustrated in FIGS. 1 to 3, the golf club head (also sometimescalled simply a “head” hereinafter) 10 is a utility type golf club head.The head has a hollow construction with an internal space, and wallsurfaces are formed by a face part 1, a crown part 2, a sole part 3, anda hosel part 4.

The face part 1 has a face surface, which is a surface that strikes aball. The crown part 2 is adjacent to the face part 1 and forms an uppersurface of the head 10. The sole part 3 mainly forms a bottom surface ofthe head 10, and constitutes the outer peripheral surface of the head 10excluding the face part 1 and the crown part 2. In other words, inaddition to the bottom surface of the head 10, a part extending from atoe side of the face part 1, across a back side of the head, and to aheel side of the face part 1 is part of the sole part 3. Furthermore,the hosel part 4 is a part provided adjacent to a heel side of the crownpart 2, and has an insertion hole 41 into which a shaft (not shown) of agolf club is inserted. A center axis line Z of the insertion hole 41coincides with an axis line of the shaft.

A reference state when the golf club head 10 is placed on a groundsurface will be described next. First, as illustrated in FIG. 2, a statein which the center axis line Z is present in a plane P1 perpendicularto the ground surface and the head is placed on the ground surface at aprescribed lie angle and real loft angle, is defined as the “referencestate”. The plane P1 is called a “reference vertical plane”. Also, asillustrated in FIG. 2, the direction of an intersecting line between thereference vertical plane P1 and the ground surface is called a “toe-heeldirection”, and a direction perpendicular to the toe-heel direction andparallel to the ground surface is called a “face-back direction”.

In the present embodiment, a boundary between the face part 1 and thecrown part 2, and a boundary between the face part 1 and the sole part3, can be defined as follows. If a ridge line is formed between theseelements, that ridge line serves as the boundary. However, if a clearridge line is not formed, the boundaries are defined as follows. In eachof cross-sections E1, E2, E3, and so on illustrated in FIG. 4A, each ofwhich contains a straight line N connecting a head center of gravity Gwith a sweet spot SS, a position Pe where a curvature radius r of a faceouter surface contour line Lf first reaches 200 mm while moving from thesweet spot side toward the face outer side, as illustrated in FIG. 4B,serves as a peripheral edge of the face part 1. This is defined as theboundary with the crown part 2 or the sole part 3. The “sweet spot SS”is a point of intersection between a normal line of the face surfacepassing through the head center of gravity G (the straight line N) andthat face surface.

Additionally, in the present embodiment, a boundary between the crownpart 2 and the sole part 3 can be defined as follows. If a ridge line isformed between the crown part 2 and the sole part 3, that ridge lineserves as the boundary. However, if a clear ridge line is not formedbetween these elements, the head is placed in the reference state and acontour seen from directly above the center of gravity of the head 10serves as the boundary.

The head 10 can be formed of, for example, a titanium alloy (Ti-6Al-4V,Ti-8Al-1Mo-1V, or the like) having a relative density of approximately4.3 to 4.5. Aside from titanium alloys, the head can be formed using oneor more of stainless steel, mariaging steel, an aluminum alloy, amagnesium alloy, an amorphous alloy, and so on, for example.

The volume of the golf club head 10 is preferably greater than or equalto 90 cm³ and less than or equal to 460 cm³, for example.

2. Assembly Structure of Golf Club Head

As illustrated in FIG. 3, the golf club head 10 according to the presentembodiment is formed by assembling a head main body 101, which includesthe crown part 2 and the sole part 3, with a face member 102, whichincludes the face part 1 and a peripheral edge part 15 extending fromthe peripheral edges of the face part 1 to form a cup-like shape. Thehead main body 101 has an opening 18 surrounded by the crown part 2 andthe sole part 3, and the face member 102 is attached so as to cover theopening 18. In other words, an end surface of the peripheral edge part15 of the face member 102 butts against an end surface of the opening 18in the head main body 101, and these are joined together by welding (forwhat is known as a “cup face construction”). The face member 102 isintegrated with the head main body 101 by being attached to the edges ofthe opening 18 in the head main body 101. As a result, the peripheraledge part 15 of the face member 102 functions as a part of the crownpart 2 and the sole part 3 of the head 10.

Accordingly, an integral surface formed by attaching the peripheral edgepart 15 of the face member 102 to the head main body 101 forms the crownpart 2 and the sole part 3 of the head 10. As such, the crown part 2 andthe sole part 3 of the head main body 101 are, strictly speaking, partsof the crown part 2 and the sole part 3 of the head 10. However, thisspecification may not make this distinction, with the parts of the headmain body 101 also being referred to simply as the crown part 2 and thesole part 3.

3. Structure of Crown Part

The crown part 2 will be described next. As illustrated in FIGS. 1 to 3,the crown part 2 includes a protruding part 21 located on the face part1 side and a base part 22 located further on the back side than theprotruding part 21. The protruding part 21 is mainly a band-shapedregion extending along the face part 1 in the toe-heel direction. On theother hand, the base part 22 is a region occupying most of the crownpart 2 at a position lower than the protruding part 21, and theperipheral edges of the base part 22 contact the sole part 3. A slopedsurface 23, which forms a step, is formed at the boundary between theprotruding part 21 and the base part 22. As such, the height of the facepart 1 in an up-down direction is higher by the size of the step betweenthe protruding part 21 and the base part 22.

The sloped surface 23 is formed so as to extend upward as the slopedsurface 23 progresses toward the face part 1. Thus when the golf clubhead 10 is placed in the reference state, the sloped surface 23 can beseen from above. In other words, the sloped surface 23 can be seen by agolfer at address position. The sloped surface 23 is formed along theprotruding part 21, and thus like the protruding part 21, is formedhaving what is a band shape when viewed in plan view.

As illustrated in FIG. 3, a width D of the protruding part 21 in theface-back direction is, for example, preferably from 5 to 25 mm andfurther preferably from 7 to 20 mm, when viewed in plan view.

Additionally, a width L of the sloped surface 23 in the face-backdirection, when viewed in plan view, is, for example, preferably from 1to 9 mm and further preferably from 2 to 7 mm. Furthermore, a height Hof the sloped surface 23 is, for example, preferably from 0.5 to 8 mm,further preferably from 0.5 to 6 mm, and particularly preferably from0.5 to 5 mm.

4. Method of Manufacturing Golf Club Head

An example of a method of manufacturing the aforementioned golf clubhead will be described next. First, the above-described head main body101 and face member 102 are prepared. The head main body 101 and theface member 102 can be manufactured through a variety of methods. Forexample, the head main body 101 can be manufactured using a knowncasting method such as lost-wax precision casting. The face member 102can be manufactured through a forging method, a process of pressing aflat plate, casting, or the like, for example. In this case, thepre-processing flat plate used for the face member 102 is processed suchthat the rolling direction substantially coincides with the directionfrom an upper part of the face part 1 on the toe side to a lower part onthe heel side.

These are then joined through welding, for example (tungsten-inert gas(TIG) welding, plasma welding, laser welding, brazing, or the like).Then, once painting or the like has been carried out, the golf club headis complete.

Note that the head according to the present embodiment is formed bycombining a head main body, which includes at least the sole part 3,with other parts. For example, the head can be formed by attaching, tothe head main body, a separate member constituting only the face part 1;or a head main body in which an opening is provided in the crown part 2can be formed, and the head can be completed by covering that openingwith a separate member.

5. Differences Between Golf Clubs in Golf Club Set

Differences between clubs in the golf club set that have different loftangles will be described next with reference to FIG. 5 as well. FIG. 5is a side view of multiple golf club heads in the reference state. FIG.5 illustrates the heads of four golf clubs, having consecutive numbers,in the golf club set according to the present embodiment as an example.These are arranged in order from left to right, from the club having thelowest loft angle, i.e., a #3 utility (U#3), a #4 utility (U#4), a #5utility (U#5), and a #6 utility (U#6). Note that in FIG. 5, the headsare illustrated in a slightly exaggerated manner to make the features ofthe invention with respect to the difference between the golf clubsclear. Thus the actual angles, shapes, and so on, which will bementioned later with reference to Table 1, are different from those inFIG. 5, but this has no effect on the essence of the invention.Furthermore, dimensions of the heads described hereinafter refer todimensions in the reference state unless otherwise specified.

As illustrated in FIG. 5, in the golf club set according to the presentembodiment, a length L, in the face-back direction, between a pointfurthest on the face side and a point furthest on the back side (calleda “head width” hereinafter), is the same in each golf club head.Specifically, a head width W can be set to a range of from 50 to 80 mm,for example. However, the heights of the heads, with the exception ofthe hosel parts 4, are different. To describe in more detail, a height Bfrom the lowermost point of the head 10 when the head 10 is arranged ona horizontal plane H, or in other words, from the horizontal plane H, tothe uppermost point of the head 10 (called a “head thickness B”hereinafter), is greater in clubs having higher loft angles. Followingthe changes in the head thickness B, a length A of face surface in theplanar direction is also greater in clubs having higher loft angles. Thevolume of the head 10 is furthermore generally greater in clubs havinghigher loft angles. Table 1 shows examples of the aforementioneddimensions and so on of these four clubs. However, Table 1 is merely anexample, and the dimension can be changed as appropriate. Note that acenter of gravity height is a height from the center of gravity of thehead in the horizontal plane H, and the SS height is a height from theSS point (sweet spot) of the head in the horizontal plane H.

TABLE 1 U#3 U#4 U#5 U#6 LOFT ANGLE (deg) 18.0 20.0 23.0 26.0 LIE ANGLE(deg) 59.5 60.0 60.5 61.0 HEAD VOLUME (cc) 114 118 121 119 A (mm) 33.034.5 36.0 36.5 B (mm) 34.0 35.0 36.0 36.0 L (mm) 65.5 65.5 65.5 65.5CENTER OF GRAVITY 11.7 12.0 12.3 12.3 HEIGHT (mm) SS HEIGHT (mm) 18.819.6 20.5 21.5

6. Effects

According to the embodiment described thus far, the following effectscan be achieved.

(1) FIG. 6 illustrates the heads of the #3 utility (U#3) and the #6utility (U#6) taken from FIG. 5, for comparative purposes. In FIG. 6,U#6, which is the club having the higher loft angle, has a higher SSpoint than U#3, which is the club having the lower loft angle. In otherwords, U#6 has a higher loft angle than U#3, and thus the SS point isgeometrically higher from the outset. However, as described above, thehead thickness B is greater as well, which raises the center of gravityG and makes the SS point even higher.

Thus when a ball 80 is struck, U#6, in which the contact point K isfurther from the SS point, rotates more easily in the Z direction (theup-down direction) about the center of gravity. The so-called geareffect increases as a result, and thus the amount of backspin, which isrotation in an SP direction, can be increased. Accordingly, clubs havinghigher loft angles, used for shots where the green is near, can increasethe amount of backspin even more. Note that utility type clubs havingloft angles of from 16 to 35 degrees as mentioned above often strikeballs located directly on the ground surface, and thus the contact pointK is often geometrically lower than the SS point.

On the other hand, the U#3 has both a low loft angle and a low headthickness, which lowers the center of gravity G and further lowers theSS point. As such, the distance between the SS point and the contactpoint K of the ball 80 is shortened, which reduces rotation in the Zdirection about the center of gravity G of the head at the time ofimpact. This not only makes it possible to suppress a drop in thehitting angle of the ball, but the SS point being closer to the contactpoint reduces the gear effect and reduces the amount of backspin, whichis rotation in the SP direction.

Accordingly, a club having a low loft angle improves the flight distanceof the ball by suppressing a drop in the hitting angle of the ball andreducing the amount of backspin. Clubs having low loft angles are usedmore often for longer shots, and thus this effect is particularlyuseful, and makes it possible to extend the flight distance of the balleven further.

Thus with the golf club set according to the present embodiment, clubshaving lower loft angles can extend the flight distances more, whereasclubs having greater loft angles can increase the amount of backspinmore.

(2) A club having a higher loft angle, such as U#6, has a greater headthickness B, which increases the moment of inertia in the up-downdirection of the head. This reduces deviation in the rotation direction,in the up-down direction of the head, at the time of impact, whichstabilizes the hitting angle of the ball. The flight distance of theball can be stabilized as a result. Clubs having high loft angles inparticular have a shorter club length and a lower head rotation radiusduring the swing, and thus compared to clubs having low loft angles,impact the ball while the head travels at a more acute angle withrespect to the grass surface. This makes it more likely for the contactpoint on the face surface to vary in the up-down direction, and morelikely for the head to deviate in the up-down rotation direction at thetime of impact. However, according to the present embodiment, deviationcan be reduced and the flight distance of the ball can be stabilized,even for clubs having high loft angles.

(3) Clubs having higher loft angles generally also have higher headvolumes, which increases the moment of inertia in the up-down direction.The same effect as that described above in (2) can thus be achieved.

(4) With the golf club set according to the present embodiment, the headwidth W is the same for all of the golf clubs. In other words, all ofthe clubs have the same head width W regardless of the loft angle. Thefollowing effects can be achieved as a result. First, a method in whichthe center of gravity G is located further on the back side, i.e., thecenter of gravity depth is increased, can be used to geometrically raisethe SS point. However, utilities are often used on the rough as well,and thus if the head width W is increased, the sole part 3 will becomelonger in the face-back direction, which increases the resistancebetween the sole part 3 and the ground surface. As such, according tothe present embodiment, as described above, resistance during the swingis reduced by keeping the head width W constant even as the loft angleis increased, while the SS point is kept high by increasing the headthickness as the loft angle is increased.

(5) In the crown part 2, the protruding part 21 is formed to be higherthan the base part 22 by using the sloped surface 23, and thus theheight of the face part 1 can be increased by the amount by which theprotruding part 21 has been made higher. This makes it possible toimprove the rebound performance at the face part 1. Additionally, onlythe protruding part 21 is formed to be higher in the crown part 2,whereas the base part 22, which occupies most of the crown part 2, isformed in a position that is lower than the protruding part 21. Thismakes it possible to lower the center of gravity of the head.

7. Variations

An embodiment of the present invention has been described thus far.However, the present invention is not intended to be limited to theabove-described embodiment. Many variations can be made thereon withoutdeparting from the essential spirit of the present invention. Thefollowing variations can also be combined as appropriate. The followingvariations are possible, for example.

7.1

Although the foregoing embodiment describes increasing the headthickness in clubs having higher loft angles, this relationship does notabsolutely have to hold true for all of the consecutive-numbered golfclubs in the golf club set. In other words, it is sufficient for thisrelationship to hold true between any of the clubs having a high loftangle and any of the clubs having a low loft angle in the golf club set.Thus, for example, in the clubs from U#3 to U#6, the relationship of thehead thicknesses B can be set to U#3<U#4=U#5<U#6, or can be set toU#3<U#4<U#5=U#6.

7.2

Although the foregoing embodiment describes the volume of the head 10generally being greater in clubs having higher loft angles, the volumeof the head 10 does not absolutely need to increase with the loft angle.For example, although the volume of the head 10 increases in order fromU#3 to U#5 in the foregoing embodiment, U#6 may have a lower volume thanU#5 and a greater volume than U#4.

7.3

Although the head widths are the same for all of the clubs in theforegoing embodiment, the head widths do not absolutely need to be thesame, and can instead be set to vary.

7.4

Although the crown part 2 of the head includes the protruding part 21 inthe foregoing embodiment, the shape of the protruding part 21 is notparticularly limited. A crown part 2 not having the protruding part 21is possible as well.

7.5

The “golf club set” according to the present invention refers to a golfclub set including the same type of golf clubs, and a single golf clubset includes only utility type golf clubs as described above. However,in addition to utility type golf clubs, the golf club set according tothe present invention can be constituted by wood type golf clubs havinghollow heads, such as drivers or fairway woods, for example.

LIST OF REFERENCE NUMERALS

-   -   1 Face part    -   2 Crown part    -   3 Sole part

What is claimed is:
 1. A golf club set constituted by a plurality ofgolf clubs having different loft angles, wherein each golf club includesa shaft and a golf club head; each of the golf club heads includes: acrown part; a face part; a sole part; and a hosel part attached to theshaft, and in at least one combination of golf clubs, among theplurality of golf clubs, having different loft angles, the golf clubhead of the golf club having the higher loft angle is, when in areference state, longer from a lowermost point to an uppermost point ofthe golf club head, excluding the hosel part, than the golf club head ofthe golf club having the lower loft angle.
 2. The golf club setaccording to claim 1, wherein the golf club head of the golf club havingthe higher loft angle has a greater volume than the golf club head ofthe golf club having the lower loft angle.
 3. The golf club setaccording to claim 1, wherein the plurality of golf club heads have thesame length, in a face-back direction, between a point furthest on aface side and a point furthest on a back side, when in the referencestate.
 4. The golf club set according to claim 1, wherein the golf clubheads are hollow wood types.
 5. The golf club set according to claim 1,wherein the loft angles of the golf club heads are from 16 to 35degrees.
 6. A golf club included in a golf club set constituted by aplurality of golf clubs having different loft angles, wherein each golfclub includes a shaft and a golf club head; each of the golf club headsincludes: a crown part; a face part; a sole part; and a hosel partattached to the shaft, and in at least one combination of golf clubs,among the plurality of golf clubs, having different loft angles, thegolf club head of the golf club having the higher loft angle is, when ina reference state, longer from a lowermost point to an uppermost pointof the golf club head, excluding the hosel part, than the golf club headof the golf club having the lower loft angle.